Current medical and aesthetic laser systems are generally considered as high-risk systems due to the fact that the light beam that is emitted from these systems has only a low divergence, or even convergence. In these systems a light beam with a high energy density and high radiance, i.e. energy density per solid angle, is generated, which hardly attenuates as the beam propagates through air, or through an air-like medium, to a distant target whereat it could cause damage to bodily tissue. In the case of a laser source emitting visible, or near visible, light, damage could result by burning a small portion of an eye retina, if the beam is accidentally aimed at the eyes of a bystander. Such beam could even cause blindness.
Potential eye damage is further increased when using near infrared lasers which emit invisible radiation, since bystanders are unaware that a laser beam is being fired. Also, the extremely short pulse duration of a beam emitted by many laser systems does not allow enough time for one to react, such as by blinking or moving the eyes, as a result of the accidental firing of a laser beam.
Therefore, in order to minimize the risk of damaging living tissues, or causing other kind of damages, special, and often, high-cost precautions must be taken. For example, such precautions might include the use of expensive (and inconvenient to use) coated protective eyeglass filters with very high optical density and damage-resistant values to optical radiation (i.e. thermal and mechanical durability). Some of the properties of such filters are included in standard documents such as ANSI Z136.1, which is the basic American National Standard document regarding the safety of laser beams. A very similar basic document which sets safety labeling standards by the food and drug administration (FDA) is $1040.10 21 CFR Ch.1. Another document which sets manufacturing standards for the safety of eyes is ISO 15004:1997E. Other precautions forbid using highly reflective surfaces in a room, where the laser system is located. Special shades and/or curtains are also utilized for preventing an accidental laser beam from escaping the room or facility, thereby protecting people outside the treatment room.
Of all the risks, the risk of permanently blinding people is the most common and severe. The currently most eye-hazardous lasers are those referred to as a pulsed-laser. For example, a Ruby, Nd:YAG, Alexandrite, LICAF, Diodes, Dye lasers, Erbium-Glass, Excimer lasers, etc. are examples of a pulsed-laser. High-class Continuous Working (CW) lasers, such as Nd:YAG, KTP and Diode lasers (at any wavelength between 630 and 1320 nm) are also known for their risk in causing blindness. Moreover, these lasers are at times used for cosmetic surgery in the vicinity of the eyes, such as for eyebrow removal or skin rejuvenation around the eyes, and therefore such surgery causes additional risk to eye damage. Other infrared lasers (pulsed and CW), such as diodes operatng at 1445 nm wavelength, CO2 and Erbium, are also capable of causing severe eye damage from a distance by burning the cornea due to the strong absorption of laser beams emitted from such laser sources in the aqueous humor of the eyeball.
There is also a risk of hair and skin burns, if the laser units are mishandled, even if operated in remote locations. Should a collimated laser beam hit a flammable material in the treatment room, a fire may result.
The risks associated with coherent lasers do not stem only from the capability to generate highly collimated beams, but also from the capability to concentrate the entire laser energy onto a confined surface from a distance, with the appropriate focusing optics.
Due to the extremely high thermodynamic temperature of lasers as electromagnetic radiation sources, as compared to the much lower temperature of conventional non-coherent light sources, the efficacy of optical intensity preservation during the focusing or imaging of laser beams, is close to 100%. Conventional non-coherent light sources, although safe to use, cannot be imaged without substantial intensity loss.
All of the above-mentioned risks associated with visible and near infrared lasers have led to very strict governmental regulations regarding the operation of medical and aesthetic laser-based systems, causing a substantial increase in the expenses of both manufacturers and operators of these systems. According to some of these governmental regulations, the operation of laser devices/systems is restricted to trained and skilled personnel, i.e. technicians or nurses under the supervision of a physician. In many countries, non-medical personnel such as cosmeticians are not allowed to handle laser-based systems at all. As a result the laser cosmetic business volume is restricted to a small fraction of its potential volume.
According to some aspects of medical and cosmetic laser systems, the treatment is focused on selected targets at the outer surface of the skin or within the skin. Each of these targets, for example, hair, vascular lesions, pigmented lesions, tattoos, acne, mild collagen damages resulting in fine wrinkles, and sun-damaged skins, have different optical spectral absorption characteristics. Therefore, these applications utilize laser systems that are capable of generating visible or near infrared light having a wavelength within the range of 310–1600 nm. There exists, therefore, a risk of directing a laser beam having an incorrect wavelength to a selected treated organ/tissue, which may severely damage this organ/tissue. Even if the organ is treated by a laser beam having the correct wavelength, there is always a risk that the laser beam might be mistakenly aimed to other areas, which are highly sensitive to the selected wavelength, thereby resulting in damage.
As opposed to laser systems, non-laser incoherent diffused sources, such as Intense Pulsed Light (IPL) sources, which are based on high voltage arc lamps, are generally considered to be damage-safe from a distance, since IPL systems have a limited light source temperature, usually in the range of 1000–10,000° C., and are consequently of limited brightness and are not focusable to small spots, in contrast to as high as 1,000,000° C. in laser systems. However, IPL systems have reduced spectral selectivity due to their broad spectral bands. Consequently, IPL-based systems offer rather limited treatment capabilities in comparison to laser-based systems.
U.S. Pat. No. 6,197,020 and U.S. Pat. No. 6,096,029 disclose imaging of a focusing, diffusing light plate, such as from the distal surface of a bundle of optical fibers at a distance beyond the system, in order to focus the beam below the tissue surface. The systems disclosed herein are also extremely risky to the eyes since the laser energy density is essentially preserved within a relatively small solid angle to which an eye may be exposed, even after having transporting the beam to a distal confined spot. As opposed to the present invention, these two patents conform to state of the art treatments by which the focusing of a laser beam to subcutaneous locations beyond the distal end of the treatment system is acceptable. The generation of a laser beam having a large divergent solid angle is disadvantageous, according to prior art methods, particularly since efficient imaging and focusing on the skin or into the skin would be precluded. Also, the laser energy density associated with these two patents is efficacious only when the diffusing, focusing plate is at a distance from a target, and is not efficacious when located adjacent to a target.
G. Vargas and A. J. Welch, in their article “Effects of Tissue Optical Clearing Agents on the Focusing Ability of Laser Light within Tissue” (“Lasers in Surgery and Medicine”, Supplement 13, 2001, p. 26) describe techniques for reducing the scattering of light energy within a tissue, in order to provide for a more focused spot and, thus, more efficient treatment of dermal lesions. However, as already described, there is a trade-off between the efficiency of a laser device and the potential risk in its operation; i.e., as the beam is more focused, the treatment becomes more risky.
Other relevant prior art is disclosed in U.S. Pat. Nos. 5,595,568, 5,879,346, 5,226,907, 5,066,293, 5,312,395, 5,217,455, 4,976,709, 6,120,497, 5,411,502, 5,558,660, 5,655,547, 5,626,631, 5,344,418, 5,964,749, 4,736.743, 5,449,354, 5,527,308, 5,814,041, 5,595,568, 5,735,844, 5,057,104, 5,282,797, 6,011,890, 5,745,519, and 6,142,650.
The prior art laser units are not capable of generating a beam with a high energy level that may be used for aesthetic or surgical procedures without presenting a risk of injury to bystanders or damage to property, such as by igniting a fire.
It is an object of the present invention to provide a laser beam that may be used for aesthetic or surgical procedures.
It is an object of the present invention to provide a laser beam that overcomes the disadvantages of the prior art.
It is another object of the present invention to provide a laser beam that is not injurious to an operator, observer or to objects located in the vicinity of or at a distance from a target.
It is an additional object of the present invention to provide a laser beam that may be used for industrial applications.
It is yet another object of the present invention to provide a unit of optical elements that provides wide angle diffusion with high thermal durability
Other objects and advantages of the invention will become apparent as the description proceeds.